OBJECTIVES (1) To determine the relationship of testosterone and DHT to prolactin during the periparturitional period. (2) To ascertain the communication of pregnancy state from female to pairbonded male and the maleUs physiological response to this condition. RESULTS While elevated prolactin levels have been associated with a reduction of fertility in both males and females, male cotton-top tamarins have elevated prolactin associated with paternal care during times when ovulation and conception are also occurring in their mates. A reciprocal relationship between testosterone has been reported for many species of mammals and birds. Our results indicate that a direct reciprocal relationship between testosterone and prolactin did not occur during the periovulatory period. However for infant-experienced males, levels of testosterone and DHT prepartum were negatively correlated with prolactin levels postpartum. Testosterone and DHT levels rose during the 10 to 15 days after birth in those males whose females were early ovulators (<20 days after birth). These data indicate that gonadal androgens do exert effects on prolactin but more discretely than what is found for birds and some rodents. The opportunity for fertility is not compromised in the tamarin where high levels of fertility is essential for the survival of the species. All fathers show different patterns of prolactin release and possibly communication between mates. Experienced fathers show elevated prolactin during the 2nd and 3rd months of their femalesU pregnancies while first-time fathers do not. This may indicate a difference in their perception of pregnancy cues from the females. Levels of cortisol, testosterone and DHT are being examined as well. While all experienced males show a prolactin rise at this time, testosterone and DHT are elevated primarily during the 5th month of pregnancy, with levels declining before birth. Inexperienced males do not show any consistent peaks in androgens during the femaleUs pregnancy. The significance of the elevated androgens in the experienced males is unknown. Cortisol levels did not change significantly in the experienced males but inexperienced males tended to have higher levels. We are collecting behavioral data on the pairbonded maleUs and pregnant femaleUs interactions to determine whether affiliation c hanges occur with these changes in hormonal patterns in experienced males. FUTURE DIRECTIONS Examine the role of neuropeptides on prolactin and parenting in tamarins KEY WORDS parental care, behaviors, prolactin, testosterone, DHT, New World primates FUNDING NIMH MH35,215 PUBLICATIONS Ziegler T.E., Snowdon C.T. The relationship of testosterone and DHT to prolactin in parental male tamarins in the periparturitional period. Society For Behavioral Neuroendocrinology, Atlanta, GA, June, 1998. [A]